Identify Garment Category

Fire an async classification of the row's garment images into the special clothing category (swimwear/underwear/kids/normal) that decides the tryon model branch.

Fire-and-forget: dispatches the identify_garment_category worker atom with a callback that backfills row.garment_category. The cell-image dialog calls this after the user picks garments into a garment cell, so the category is resolved up front instead of relying solely on the generate-time fallback. Returns immediately; the result lands via the /api/internal/tryon/rows/{id}/garment-category-result callback.